Polyester resin, method for preparing same, and resin molded product formed therefrom

ABSTRACT

The present invention relates to a polyester resin. The polyester resin contains a particular content of diol moieties, derived from isosorbide and diethylene glycol, and thus can provide a resin molded product exhibiting high transparency in spite of a large wall thickness thereof.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of priority from Korean PatentApplication No. 10-2017-0067962 filed on May 31, 2017 with the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a polyester resin capable of providinga resin molded article exhibiting high transparency despite its thickthickness, a method for preparing the same, and a resin molded articleformed therefrom.

BACKGROUND

PET (polyethylene terephthalate) represented by a polyester resin iswidely used for commercial purposes due to its low price and excellentphysical/chemical properties. However, it has high crystallinity andthus requires a high temperature during processing, and there is aproblem that transparency of a molded article is lowered. In addition,the PET has poor heat resistance and so cause a problem that the shapeof a bottle molded with PET is deformed during high temperature fillingof a beverage. In order to prevent this, an attempt is made to increasethe heat resistance of the bottle through a bottleneck crystallizationprocess and a heat setting process before and after the bottleformation, but the transparency of the bottle is decreased.

In order to overcome these problems, techniques have been developed toincrease the glass transition temperature of PET by copolymerizingvarious monomers.

Among them, isosorbide is a vegetable raw material, can increase theglass transition temperature and improve the mechanical strength afterthe solid phase polymerization. Due to these advantages, isosorbide hasattracted attention as a comonomer applicable to PET.

However, as the content of isosorbide is higher to increase the heatresistance, the regularity of the polymer chains is lowered and thecrystallization rate is decreased. Further, when the added amount ofisosorbide exceeds a certain level, it cannot function as a crystallineresin. Since the non-crystalline resin cannot be drawn, in order to formthe non-crystalline resin into a bottle, it is necessary to design thelength of a preform to be similar to the length of the bottle. As aresult, it becomes impossible to use the equipment for processing theexisting PET resin, and there is a great obstacle in actuallymanufacturing a resin molded article by using a copolymer usingisosorbide.

Technical Problem

The present invention provides a polyester resin and a method forpreparing the same.

The present invention provides a resin molded article formed from thepolyester resin and exhibiting high transparency even if it is preparedwith a thick thickness.

Technical Solution

In order to achieve the objects above, according to one embodiment ofthe present invention, there is provided a polyester resin polymerizedwith a dicarboxylic acid including terephthalic acid or a derivativethereof and a diol including isosorbide and ethylene glycol, therebyhaving an alternating structure of an acid moiety derived from thedicarboxylic acid or a derivative thereof and a diol moiety derived fromthe diol, wherein the polyester resin includes 6 to 12 mol % of a diolmoiety derived from isosorbide and 2 to 5 mol % of a diol moiety derivedfrom diethylene glycol based on the total diol moieties derived from thediol, wherein a melting point exists during the first scan through adifferential scanning calorimetry (DSC), and wherein a haze is less than3% as measured according to ASTM D1003-97 for a specimen having athickness of 6 mm obtained from the polyester resin.

According to another embodiment of the present invention, there isprovided a preparation method of the polyester resin and a moldedarticle prepared from the polyester resin.

Advantageous Effects

The polyester resin according to one embodiment of the present inventionhas a melting point during the first scan through DSC and so can beformed by drawing. The polyester resin is prepared with a specimenhaving a thickness of 6 mm and exhibits a haze of less than 3%, therebyenabling the provision of a transparent resin molded article even whilehaving a thick thickness. Therefore, the polyester resin can provide aresin molded article suitable for various uses such as a hot fill jarand a high-pressure vessel.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a polyester resin, a preparation method thereof, and aresin molded article prepared therefrom according to specificembodiments of the invention will be described.

Unless otherwise specified, the terminology used herein is for thepurpose of describing particular embodiments only and is not intended tolimit the scope of the invention. Further, the singular forms “a,” “an”and “the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. In addition, it will be furtherunderstood that the meaning of the terms “comprise”, “include” as usedherein is intended to specify the presence of stated features, ranges,integers, steps, operations, elements and/or components, but does notpreclude the presence or addition of other features, ranges, integers,steps, operations, elements and/or components.

According to one embodiment of the present invention, there is provideda polyester resin polymerized with a dicarboxylic acid includingterephthalic acid or a derivative thereof and a diol includingisosorbide and ethylene glycol, thereby having an alternating structureof an acid moiety derived from the dicarboxylic acid or a derivativethereof and a diol moiety derived from the diol, wherein the polyesterresin includes 6 to 12 mol % of a diol moiety derived from isosorbideand 2 to 5 mol % of a diol moiety derived from diethylene glycol basedon the total diol moieties derived from the diol, wherein a meltingpoint exists during the first scan through a differential scanningcalorimetry (DSC), and wherein a haze is less than 3% as measuredaccording to ASTM D1003-97 for a specimen having a thickness of 6 mmobtained from the polyester resin.

In the case of PET which is represented by a polyester resin, theregularity of the polymer chain is high and a crystal is formed, wherebya melting point exists during the first scan through DSC. However, sincePET has a low glass transition temperature, its use in applicationsrequiring high heat resistance such as hot fill bottles has beenlimited.

In order to solve these problems, a method of introducing isosorbideinto the backbone of conventional polymers has been introduced. However,residues derived from isosorbide deteriorated the regularity of thepolymer chain, which in turn deteriorated the crystallization rate ofthe resin. In order to ensure sufficient heat resistance, the polyesterresin should contain a large amount of diol moieties derived fromisosorbide, but this caused a problem that the polyester resin could notfunction as a crystalline resin due to the large amount of diol moietiesderived from isosorbide. In addition, non-crystalline resins have lowregularity of the molecular structure and so cannot be formed bydrawing, and in particular, existing PET processing equipment cannot beused. Due to these problems, there was a limitation on the content ofisosorbide that can be introduced into the polymer backbone.

On the other hand, when the introduced amount of isosorbide is less than6 mol % which is insufficient, the glass transition temperature is lessthan 85° C., so that it does not exhibit a sufficient heat resistance.Usually, in order to be applied to applications such as a hot fill jar,the glass transition temperature is required to be at least 85° C., andso the low content of isosorbide cannot achieve the target level interms of heat resistance.

In order to solve these problems and the like, in the case of the PETresin, the heat resistance and the mechanical strength can be improvedthrough an additional heat treatment process after injection molding. Inthis case, however, the crystals produced by the heat cause a haze inthe product, and generally the haze is observed even with the naked eye,and there was a limitation in its use for food containers and bottle.

Despite these technical limitations, the polyester resin according tothis embodiment contains the above-mentioned ranges of diol moietiesderived from isosorbide and diethylene glycol, and thus can provide aresin molded article exhibiting high transparency despite its thickthickness, while exhibiting excellent heat resistance and mechanicalproperties.

In addition, since the polyester resin according to one embodiment ofthe present invention has a melting point during the first scan throughDSC and can be formed by drawing, there is an advantage in that existingPET processing equipment can be used.

In the case of PET resin, the crystallization rate is very high, andwhen formed to a thick thickness, haze is generated. In particular, itis difficult to transparently prepare a specimen having a thickness of 6mm with PET resin.

In contrast, the polyester resin according to one embodiment of thepresent invention may have a haze of less than 3%, less than 2.5%, lessthan 2%, less than 1.5%, or less than 1.0% as measured according to ASTMD1003-97 when prepared into a specimen having a thickness of 6 mm. Whenthe polyester resin according to one embodiment of the present inventionis prepared into a specimen having a thickness of 6 mm, no haze may beobserved. Thus, the lower limit of the haze may be 0%.

Hereinafter, a method for preparing such polyester resin will bedescribed in detail.

The polyester resin may be prepared by the method comprising the stepsof:

(a) carrying out an esterification reaction or a transesterificationreaction of (i) a dicarboxylic acid or a derivative thereof includingterephthalic acid or a derivative thereof and (ii) a diol including 6.5mol to 25 mol of isosorbide and 80 mol to 200 mol of ethylene glycolbased on 100 mol of the total dicarboxylic acid or a derivative thereof;and

(b) subjecting the esterification or transesterification reactionproduct to a polycondensation reaction so that an intrinsic viscosity,which is measured at 35° C. after dissolving the reaction product inorthochlorophenol at a concentration of 1.2 g/dl at 150° C. for 15minutes, reaches 0.45 dl/g to 0.75 dl/g.

More specifically, the polyester resin is obtained by (a) carrying outan esterification reaction or a transesterification reaction of (i) thedicarboxylic acid or a derivative thereof and (ii) the diol under apressure of 0 to 10.0 kgf/cm² (absolute pressure of 0 to 7355.6 mmHg)and a temperature of 150 to 300° C. for an average residence time of 1to 24 hours, and then (b) subjecting the esterification ortransesterification reaction product to a polycondensation reactionunder a reduced pressure condition of 400 to 0.01 mmHg at a temperatureof 150 to 300° C. for an average residence time of 1 to 24 hours.

Herein, the preparation method of the polyester resin may be carried outas a batch process, a semi-continuous process or a continuous process,and the esterification reaction or transesterification reaction and thepolycondensation reaction are preferably carried out under an inert gasatmosphere, the mixing of the polyester resin with other additives maybe simple mixing or mixing by extrusion.

In addition, if necessary, a solid phase polymerization reaction mayproceed in succession. Specifically, the method for preparing thepolyester resin according to one embodiment of the present invention mayfurther include, after step (b), (c) a step of crystallizing the polymerprepared by polycondensation reaction (melt polymerization); and (d) astep of subjecting the crystallized polymer to a solid phasepolymerization such that the intrinsic viscosity, which is measured at35° C. after dissolving the polymer in orthochlorophenol at aconcentration of 1.2 g/dl at 150° C. for 15 minutes, reaches a value of0.10 to 0.40 dl/g higher than the intrinsic viscosity of the resinobtained in step (b).

As used herein, the term “dicarboxylic acid or a derivative thereof”means at least one compound selected from dicarboxylic acid and aderivative of dicarboxylic acid. The term “derivative of dicarboxylicacid” means an alkyl ester of dicarboxylic acid (lower alkyl esterhaving 1 to 4 carbon atoms such as monomethyl, monoethyl, dimethyl,diethyl or dibutyl ester, etc.) or an anhydride of dicarboxylic acid.Thus, for example, terephthalic acid or a derivative thereof iscollectively referred to as terephthalic acid; monoalkyl or dialkylterephthalate; and compounds of forming a terephthaloyl moiety byreaction with diols, such as terephthalic acid anhydride.

As the (i) dicarboxylic acid or derivatives thereof, terephthalic acidor a derivative thereof is mainly used. Specifically, terephthalic acidor a derivative thereof may be used alone as the (i) dicarboxylic acidor derivatives thereof. Further, the (i) dicarboxylic acid orderivatives thereof may be used in the form of a mixture of terephthalicacid or a derivative thereof; and at least one selected from the groupconsisting of an aromatic dicarboxylic acid having 8 to 14 carbon atomsor a derivative thereof and an aliphatic dicarboxylic acid having 4 to12 carbon atoms or a derivative thereof, which is a dicarboxylic acid ora derivative thereof other than the terephthalic acid or a derivativethereof. The aromatic dicarboxylic acid having 8 to 14 carbon atoms or aderivative thereof may include an aromatic dicarboxylic acid or aderivative thereof commonly used in the preparation of polyester resins,for example, naphthalene dicarboxylic acid such as isophthalic acid,dimethyl isophthalate, phthalic acid, dimethyl phthalate, phthalicanhydride, 2,6-naphthalene dicarboxylic acid or the like, dialkylnaphthalene dicarboxylate such as dimethyl 2,6-naphthalenedicarboxylate, or the like, diphenyldicarboxylic acid, and the like. Thealiphatic dicarboxylic acid having 4 to 12 carbon atoms or a derivativethereof may include a linear, branched or cyclic aliphatic dicarboxylicacid or a derivative thereof conventionally used in the preparation ofpolyester resins, for example, cyclohexanedicarboxylic acid such as1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, orthe like, cyclohexanedicarboxylate such as dimethyl1,4-cyclohexanedicarboxylate, dimethyl 1,3-cyclohexanedicarboxylate orthe like, sebacic acid, succinic acid, isodecyl succinic acid, maleicacid, maleic anhydride, fumaric acid, adipic acid, glutaric acid,azelaic acid, and the like.

The (i) dicarboxylic acid or a derivative thereof may includeterephthalic acid or a derivative thereof in an amount of 50 mol % ormore, 60 mol % or more, 70 mol % or more, 80 mol % or more, or 90 mol %or more based on the total (i) dicarboxylic acids or derivativesthereof. The (i) dicarboxylic acid or a derivative thereof may include adicarboxylic acid or a derivative thereof other than terephthalic acidor a derivative thereof in an amount of 0 to 50 mol %, greater than 0mol % and 50 mol % or less, or 0.1 to 40 mol % based on the total (i)dicarboxylic acids or derivatives thereof. Within such a content range,the polyester resin realizing appropriate physical properties can beprepared.

Meanwhile, the isosorbide (1,4:3,6-dianhydroglucitol) is used such thatthe diel moiety derived from isosorbide is 6 to 12 mol based on thetotal diol moieties derived from the diol of the polyester resinprepared.

A part of isosorbide may be volatilized or not reacted during thesynthesis of the polyester resin. Therefore, in order to introduce theabove-mentioned content of isosorbide into the polyester resin, theisosorbide may be used in an amount of or 6.5 mol to 25 mol based on 100mol of the total dicarboxylic acids or derivatives thereof.

If the content of isosorbide exceeds the above range, a melting pointdoes not exist during the first scan through DSC and so processing bydrawing becomes difficult. If the content is less than the above range,sufficient heat resistance and mechanical strength may not be exhibited,and a haze may generate. However, when the content of isosorbide isadjusted within the above-mentioned range, a melting point exists duringthe first scan through DSC, and when prepared into a specimen having athickness of 6 mm, the polyester resin exhibiting high transparency canbe provided.

The content of the diol moiety derived from diethylene glycol introducedinto the polyester resin is not directly proportional to the content ofethylene glycol used for the preparation of the polyester resin.However, ethylene glycol may be used in an amount of 80 mol to 200 molbased on 100 mol of the total dicarboxylic acids or derivatives thereofso that the diol moiety derived from diethylene glycol is 2 to 5 mol %based on the total diol moieties derived from the diol of the polyesterresin.

If the content of the diol moiety derived from diethylene glycolintroduced into the polyester resin exceeds the above range, it may notexhibit sufficient heat resistance, and if the content is less than theabove range, a haze may generate.

The (ii) diol may include a compound commonly used in the preparation ofpolyester resins as the diol other than isosorbide, and examples thereofinclude an aromatic diol having 8 to 40 carbon atoms or 8 to 33 carbonatoms. an aliphatic diol having 2 to 20 carbon atoms or 2 to 12 carbonatoms, or a mixture thereof.

Specific examples of the aromatic diol include bisphenol A derivativesadded with ethylene oxide and/or propylene oxide(polyoxyethylene-(n)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(n)-2,2-bis(4-hydroxyphenyl)propane orpolyoxypropylene-(n)-polyoxyethylene-(n)-2,2-bis(4-hydroxyphenyl)propane,wherein n represents the number of polyoxyethylene unit orpolyoxypropylene unit), such aspolyoxyethylene-(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.2)-polyoxyethylene-(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxyethylene-(2.3)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(6)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.3)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.4)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(3.3)-2,2-bis(4-hydroxyphenyl)propane,polyoxyethylene-(3.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxyethylene-(6)-2,2-bis(4-hydroxyphenyl)propane, and so on. Specificexamples of the aliphatic diol include linear, branched or cyclicaliphatic diol components such as ethylene glycol, diethylene glycol,triethylene glycol, propanediol (1,2-propanediol, 1,3-propanediol and soon), 1,4-butanediol, pentanediol, hexanediol (1,6-hexanediol and so on),neopentyl glycol (2,2-dimethyl-1,3-propandiol), 1,2-cyclohexanediol,1,4-cyclohexanediol, 1,2-cyclohexanedimethanol,1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol,tetramethylcyclobutanediol and so on. Specific examples of the aliphaticdiol include a linear, branched or cyclic aliphatic diol such asdiethylene glycol, triethylene glycol, propanediol (1,2-propanediol,1,3-propanediol or the like), 1,4-butanediol, pentanediol, hexanediol(1,6-hexanediol, or the like), neopentyl glycol(2,2-dimethyl-1,3-propanediol), 1,2-cyclohexanediol,1,4-cyclohexanediol, 1,2-cyclohexanedimethanol,1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol,tetramethylcyclobutanediol or the like. As the (ii) diol, theabove-listed diols other than the isosorbide and ethylene glycol can beincluded alone or in combination of two or more thereof. For example,1,4-cyclohexanedimethanol,polyoxyethylene-(2.0)-2,2-bis(4-hydroxyphenyl)propane or the like may beadded alone or in combination of two or more thereof to the isosorbideand ethylene glycol. In the (ii) diol, the content of the diol used forimproving the physical properties in addition to isosorbide and ethyleneglycol may be adjusted, for example, to 0 to 50 mol % or 0.1 to 30 mol%, based on the total (ii) diols.

In order to prepare the polyester resin according to one embodiment, the(i) dicarboxylic acid or a derivative thereof and the (ii) diol may beadded to a reactor so that the molar ratio between the (i) dicarboxylicacid or a derivative thereof and the (ii) diol is 1.01 or more. Inaddition, the (ii) diol may be supplied to the reactor at one timebefore the polymerization reaction or may be added during thepolymerization reaction several times, if necessary.

According to a more specific embodiment, the polyester resin satisfyinga specific molecular weight distribution may be prepared by adjustingthe initial input amount of the (i) dicarboxylic acid or a derivativethereof and the (ii) diol in the initial stage of a reaction. Thereby,the polyester resin of one embodiment can be more effectively obtained.

In one example, when a dicarboxylic acid is used as the (i) dicarboxylicacid or a derivative thereof, the initial mixing molar ratio between the(i) dicarboxylic acid or a derivative thereof and the (ii) diol may beadjusted to 1:1.01 to 1.05, and when a derivative such as a dicarboxylicacid alkyl ester or a dicarboxylic acid anhydride is used as the (i)dicarboxylic acid or a derivative thereof, the initial mixing molarratio between the (i) dicarboxylic acid derivative and the (ii) diol maybe adjusted to 1:2.0 to 1:2.1.

The initial mixing molar ratio may refer to a mixing molar ratio at thestart of the polymerization reaction in the reactor, and (i)dicarboxylic acid or a derivative and/or (ii) diol may be further addedduring the reaction if necessary.

Meanwhile, a catalyst may be used in the (a) esterification reaction ortransesterification reaction. Examples of the catalyst include amethylate of sodium and magnesium; an acetate, a borate, a fatty acidsalt, a carbonate, and an alkoxy salt of Zn, Cd, Mn, Co, Ca, Ba, Ti orthe like; metal Mg; an oxide of Pb, Zn, Sb, Ge, or the like.

The (a) esterification reaction or the transesterification reaction maybe performed as a batch process, a semi-continuous process or acontinuous process, and each raw material may be added separately, butit may be preferably added in the form of a slurry in which thedicarboxylic acid or a derivative thereof is mixed to the diol.

A polycondensation catalyst, a stabilizer, a coloring agent, acrystallizing agent, an antioxidant, a branching agent and the like maybe added to the slurry before the start of the (a) esterificationreaction or the transesterification reaction, or to the product afterthe completion of the reaction.

However, the timing of adding the above-described additives is notlimited thereto, and they may be added at any time point during thepreparation of the polyester resin. As the polycondensation catalyst, atleast one of conventional titanium-based catalyst, germanium-basedcatalyst, antimony-based catalyst, aluminum-based catalyst, tin-basedcatalyst, or the like may be appropriately selected and used. Examplesof the useful titanium-based catalyst include tetraethyl titanate,acetyltripropyl titanate, tetrapropyl titanate, tetrabutyl titanate,polybutyl titanate, 2-ethylhexyl titanate, octylene glycol titanate,lactate titanate, triethanolamine titanate, acetylacetonate titanate,ethyl acetoacetic ester titanate, isostearyl titanate, titanium dioxide,titanium dioxide/silicon dioxide copolymer, titanium dioxide/zirconiumdioxide copolymer or the like. Further, examples of the usefulgermanium-based catalyst include germanium dioxide and a copolymerthereof. As the stabilizer, generally, a phosphor-based stabilizer suchas phosphoric acid, trimethyl phosphate, triethyl phosphate, or the likemay be used, and the added amount thereof may be in the range of 10 ppmto 200 ppm relative to the weight of the final polymer (polyester resin)based on the amount of phosphorus atom. If the added amount of thestabilizer is less than 10 ppm, the polyester resin may not besufficiently stabilized and the color of the polyester resin may becomeyellow. If the amount of phosphor is more than 200 ppm, a desiredpolymer having a high degree of polymerization may not be obtained.Examples of the coloring agent added for improving the color of thepolymer include a cobalt-based decoloring agent such as cobalt acetate,cobalt propionate or the like, and the added amount thereof is 10 to 200ppm relative to the weight of the final polymer (polyester resin) basedon the amount of cobalt atom. If necessary, as an organic coloringagent, an anthraquionone-based compound, a perinone-based compound, anazo-based compound, a methine-based compound and the like may be used.Commercially available products include a toner such as polysynthreneBlue RLS manufactured by Clarient or Solvaperm Red BB manufactured byClarient. The added amount of the organic coloring agent may be adjustedin the range of 0 to 50 ppm relative to the weight of the final polymer.If the coloring agent is used in an amount outside the above range, theyellow color of the polyester resin may not be sufficiently concealed orthe physical properties may be deteriorated.

Examples of the crystallizing agent include a crystal nucleating agent,an UV absorber, a polyolefin-based resin, a polyamide resin or the like.Examples of the antioxidant include a hindered phenol-based antioxidant,a phosphite-based antioxidant, a thioether-based antioxidant, or amixture thereof. As the branching agent, for example, trimelliticanhydride, trimethylol propane, trimellitic acid or a mixture thereofmay be used as a conventional branching agent having three or morefunctional groups.

The (a) esterification reaction or the transesterification reaction maybe carried out at a temperature of 150 to 300° C. or 200 to 270° C.under a pressure condition of 0 to 10.0 kgf/cm² (0 to 7355.6 mmHg), 0 to5.0 kgf/cm² (0 to 3677.8 mmHg) or 0.1 to 3.0 kgf/cm² (73.6 to 2206.7mmHg). Here, the pressure stated in the outside of the parenthesisrefers to a gauge pressure (expressed in kgf/cm²); and the pressurestated in the parenthesis refers to an absolute pressure (expressed inmmHg).

If the reaction temperature and pressure deviate from the above range,the physical properties of the polyester resin may be deteriorated. Thereaction time (average retention time) is usually 1 to 24 hours or 2 to8 hours, and may vary depending on the reaction temperature, thepressure, and the molar ratio of the dicarboxylic acid or a derivativethereof to the diol used.

The product obtained by the esterification or the transesterificationreaction may be prepared into a polyester resin having a higher degreeof polymerization by polycondensation reaction. Generally, thepolycondensation reaction is carried out at a temperature of 150 to 300°C., 200 to 290° C. or 250 to 290° C. under a reduced pressure of 0.01 to400 mmHg, 0.05 to 100 mmHg or 0.1 to 10 mmHg. Herein, the pressurerefers to the range of absolute pressures. The reduced pressure of 0.01mmHg to 400 mmHg is used to remove glycol as a by-product of thepolycondensation reaction, and isosorbide as an unreacted material, etc.Thus, if the reduced pressure condition deviates from the above range,the by-products and unreacted materials may not be sufficiently removed.Moreover, if the temperature of the polycondensation reaction deviatesfrom the above range, the physical properties of the polyester resin maybe deteriorated. The polycondensation reaction is carried out for aperiod of time required to reach a desirable intrinsic viscosity, forexample, it may be carried out for an average retention time of 1 hoursto 24 hours.

For the purpose of reducing the amount of unreacted materials such asisosorbide remaining in the polyester resin, it is possible tointentionally increase the vacuum reaction at the last stage of theesterification reaction or transesterification reaction or at theinitial stage of the polycondensation reaction, that is, at a state inwhich the viscosity of the resin is not sufficiently high, therebydischarging the unreacted raw materials out of the system. When theviscosity of the resin is increased, it may be difficult for rawmaterials remaining in the reactor to escape out of the system. In oneexample, before the polycondensation reaction, the reaction productobtained by the esterification reaction or the transesterificationreaction is allowed to stand at a reduced pressure condition of about400 to 1 mmHg or about 200 to 3 mmHg for 0.2 to 3 hours to effectivelyremove unreacted materials such as isosorbide remaining in the polyesterresin. Herein, the temperature of the product may be controlled to atemperature equal to the temperature of the esterification reaction ortransesterification reaction and of the polycondensation reaction, or toa temperature therebetween.

As the process of flowing out the unreacted raw materials through thecontrol of the vacuum reaction is further added, the amount of unreactedmaterials such as isosorbide remaining in the polyester resin can bereduced, and consequently, the polyester resin satisfying the physicalproperties of one embodiment can be more effectively obtained.

Meanwhile, the intrinsic viscosity of the polymer after thepolycondensation reaction is appropriately in the range of 0.45 dl/g to0.75 dl/g.

In particular, if the crystallization step (c) and the solid phasepolymerization step (d) described above are employed, the intrinsicviscosity of the polymer after the polycondensation reaction can beadjusted to 0.45 to 0.75 dl/g, 0.45 to 0.70 dl/g or 0.50 to 0.65 dl/g.If the intrinsic viscosity of the polymer after the polycondensationreaction is less than 0.45 dl/g, the reaction speed in the solid phasepolymerization reaction is significantly reduced, and a polyester resinhaving a very high molecular weight distribution is obtained. If theintrinsic viscosity exceeds 0.75 dl/g, as the viscosity of the meltincreases during the melt polymerization, the possibility ofdiscoloration of the polymer is increased due to the shear stressbetween the stirrer and the reactor, and side reaction materials such asacetaldehyde are also increased. Further, the crystallization rate isremarkably slowed, and fusion occurs during the crystallization process,and the shape of the pellet is liable to be deformed.

Meanwhile, if the crystallization step (c) and the solid phasepolymerization step (d) described above are not employed, the intrinsicviscosity of the polymer after the polycondensation reaction may beadjusted to 0.65 to 0.75 dl/g. If the intrinsic viscosity is less than0.65 dl/g, the crystallization rate increases due to the low molecularweight polymer, and so it may be difficult to provide a polyester resinhaving excellent heat resistance and transparency. If the intrinsicviscosity exceeds 0.75 dl/g, as the viscosity of the melt increasesduring the melt polymerization, the possibility of discoloration of thepolymer is increased due to the shear stress between the stirrer and thereactor, and side reaction materials such as acetaldehyde are alsoincreased.

A polyester resin according to one embodiment can be produced throughthe steps (a) and (b). If necessary, the crystallization step (c) andthe solid phase polymerization step (d) may be further carried out afterthe (b) polycondensation reaction to provide a polyester resin having ahigher degree of polymerization.

Specifically, in the crystallization step (c), the polymer obtained bythe polycondensation reaction (b) is discharged out of the reactor to begranulated. As the granulation method, a strand cutting method ofextruding into a strand type, solidifying in a cooling liquid and thencutting with a cutter, or an underwater cutting method of immersing adie hole in a cooling liquid, directly extruding in a cooling liquid andthen cutting with a cutter can be used. Generally, in the strand cuttingmethod, the cooling liquid is maintained at a low temperature to enablethe solidification of the strand, thereby preventing cutting problems.In the underwater cutting method, it is preferred that the temperatureof the cooling liquid is maintained in accordance with the polymer sothat the shape of the polymer becomes uniform. However, in the case of acrystalline polymer, the temperature of the cooling liquid may beintentionally maintained at a high level in order to inducecrystallization during discharge.

Meanwhile, it is also possible to additionally wash the granulatedpolymer with water. The temperature of water during washing ispreferably equal to or lower by about 5 to 20° C. than the glasstransition temperature of the polymer, and fusion may occur at a highertemperature, which is not preferable. In the case of polymer particlesthat induce the crystallization during discharge, fusion does not occurat a temperature higher than the glass transition temperature, and thus,the temperature of water may be set according to the degree ofcrystallization. Through washing of the granulated polymer, the rawmaterials dissolved in water among the unreacted raw materials can beremoved. As the particle size decreases, the surface area relative tothe weight of the particles increases, and thus, a smaller particle sizeis preferred. In order to achieve such purpose, the particles may beprepared to have an average weight of about 14 mg or less.

The granulated polymer undergoes the crystallization step to preventfusion during the solid phase polymerization. The crystallization may becarried out under the atmosphere, inert gas, water vapor,vapor-containing inert gas atmosphere or in a solution at 110° C. to180° C. or 120° C. to 180° C. If the temperature is low, the rate atwhich the crystals of the particles are formed is too slow. If thetemperature is high, the particles are melted at a faster rate than therate at which the crystals are formed, making the particles to sticktogether, thereby causing fusion to occur. Since the heat resistance ofthe particles increases as the particles are crystallized, it is alsopossible to carry out the crystallization by dividing it into severalsteps and raising the temperature stepwise.

The solid phase polymerization reaction may be carried out under aninert gas atmosphere such as nitrogen, carbon dioxide, argon or thelike, or under a reduced pressure condition of 400 to 0.01 mmHg at atemperature of 180° C. to 220° C. for an average retention time of 1hour or more, preferably 10 hours or more. This solid phasepolymerization further increases the molecular weight, and the rawmaterials, which remain unreacted in the melting reaction, and cyclicoligomers, acetaldehydes and the like generated during the reaction maybe removed.

In order to provide the polyester resin according to one embodiment, thesolid phase polymerization may be carried out until the intrinsicviscosity reaches a value of 0.10 dl/g to 0.40 dl/g higher than theintrinsic viscosity of the resin obtained in the polycondensationreaction step (b). If the difference between the intrinsic viscosity ofthe resin after the solid phase polymerization reaction and theintrinsic viscosity of the resin before the solid phase polymerizationis less than 0.10 dl/g, a sufficient degree of polymerization improvingeffect cannot be obtained. If the difference between the intrinsicviscosity of the resin after the solid phase polymerization and theintrinsic viscosity of the resin before the solid phase polymerizationexceeds 0.40 dl/g, the molecular weight distribution becomes wide and soa sufficient heat resistance cannot be exhibited, and further thecontent of the low molecular weight polymer is relatively increased andthe crystallization rate is increased, and thereby the possibility ofgeneration of a haze is increased.

The solid phase polymerization is carried out until the intrinsicviscosity of the resin is 0.10 to 0.40 dl/g higher than the intrinsicviscosity of the resin before the solid phase polymerization, and theintrinsic viscosity reaches a value of 0.70 dl/g or more, 0.70 to 1.0dl/g, or 0.70 to 0.95 dl/g. When the solid phase polymerization iscontinued until it reaches the intrinsic viscosity within such range,the molecular weight distribution of the polymer becomes narrower,thereby decreasing the crystallization rate during molding. Accordingly,the heat resistance and the degree of crystallinity can be improvedwithout deteriorating the transparency. If the intrinsic viscosity ofthe resin after the solid phase polymerization reaction is less than theabove range, it may be difficult to provide a polyester resin havingexcellent heat resistance and transparency due to an increase in thecrystallization rate by the low molecular weight polymer.

The polyester resin prepared by the above method has an alternatingstructure of an acid moiety derived from a dicarboxylic acid or aderivative thereof and a diol moiety derived from a diol. In thespecification, the acid moiety and the diol moiety refers to a residueremaining after the dicarboxylic acid or a derivative thereof and thediol are polymerized and hydrogen, hydroxyl or alkoxy groups are removedtherefrom.

In particular, the polyester resin is prepared according to the methoddescribed above, whereby a diol moiety derived from isosorbide is 6 to12 mol %, and a diol moiety derived from diethylene glycol is 2 to 5 mol%, based on the total diol moieties derived from the diol, a meltingpoint exists during the first scan through a differential scanningcalorimetry (DSC), and a haze is less than 3% when prepared into aspecimen having a thickness of 6 mm.

The diol moiety derived from the diethylene glycol may be thatintroduced by reaction of two ethylene glycols to form diethyleneglycol, and then reaction of such diethylene glycol with a dicarboxylicacid or a derivative thereof. As the polyester resin according to oneembodiment of the present invention is prepared by the above-mentionedmethod, it includes a diol moiety derived from diethylene glycol in theabove-mentioned content range, thereby providing a resin molded articlehaving excellent heat resistance and mechanical properties andexhibiting high transparency despite its thick thickness.

The polyester resin may have a number average molecular weight (Mn) ofabout 15,000 to 50,000 g/mol or about 18,000 to 40,000 g/mol. Thepolyester resin may have a weight average molecular weight (Mw) of50,000 to 150,000 g/mol or 60,000 to 110,000 g/mol. Further, themolecular weight distribution (PDI) of the polyester resin may be in therange of 2.5 to 4.0 or 2.8 to 3.85.

If the molecular weight is less than the above range, it is difficult tosecure desired mechanical properties because sufficient drawing is notmade when developed into a bottle, sheet, multilayer sheet, drawn filmor fiber. If the molecular weight exceeds the above range, the moldingprocessability may be deteriorated. On the other hand, when themolecular weight distribution is adjusted within the above-mentionedrange, the relative content of the low molecular weight polymer is smalland the crystallization rate is sufficiently slow, so that the heatresistance and transparency of the resin molded article are improved.

The polyester resin may have a melting point (Tm) of about 200 to 250°C., about 200 to 240° C., or 210 to 236° C., as measured during thefirst scan through a differential scanning calorimetry (DSC). Withinthis range, the polyester resin has appropriate crystallinity, exhibitsgood heat resistance and mechanical properties, can be processed at anappropriate temperature, and thus there is no possibility of yellowing.

The polyester resin may have a glass transition temperature (Tg) of 85°C. or more, or 85° C. to 95° C., or 85° C. to 92° C. Within this range,it can be used for applications such as hot fill jar, and variousphysical properties of the polyester resin can be favorably exhibitedwithout a yellowing phenomenon.

As described above, the polyester resin according to one embodiment ofthe present invention can provide a resin molded article havingexcellent heat resistance and mechanical properties, and exhibiting hightransparency while having a thick wall thickness. Accordingly, thepolyester resin can be utilized in various fields, and in particular,because of its excellent heat resistance and transparency, it isexpected to be useful for applications in a bottle, a hot fill jar, ahigh-pressure vessel, a sheet, a drawn film and a fiber.

Meanwhile, according to anther embodiment of the present invention,there is provided a molded article formed from the polyester resin. Theresin molded article may have a very thick wall thickness of 4.5 mm ormore, 4.5 mm to 30 mm, 4.5 mm to 10 mm, 4.5 mm to 7 mm, or about 6 mm.Nevertheless, the resin molded article can exhibit very hightransparency. The resin molded article may be a bottle, a hot fill jar,a high-pressure vessel, a sheet, a drawn film, a fiber, or the like.

Hereinafter, the action and effect of the present invention will bedescribed by way of specific Examples. However, these Examples are givenfor illustrative purposes only, and they are not intended to limit thescope of the invention in any manner.

The following physical properties were measured according to the methodsbelow.

(1) Intrinsic viscosity (IV): The intrinsic viscosity of the specimenwas measured using an Ubbelohde viscometer after dissolving the specimenin orthochlorophenol (OCP) at a concentration of 1.2 g/dl at 150° C. for15 minutes. Specifically, the temperature of the viscometer wasmaintained at 35° C. and the time (efflux time) to required for asolvent to pass between the specific internal sections of the viscometerand the time t required for a solution to pass therebetween weredetermined. Thereafter, the value of to and the value of t weresubstituted into Equation 1 to calculate a specific viscosity, and thecalculated specific viscosity value was substituted into Equation 2 tocalculate an intrinsic viscosity.

$\begin{matrix}{\eta_{sp} = \frac{t - t_{0}}{t_{0}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack \\{\lbrack\eta\rbrack = \frac{\sqrt{1 + {4A\; \eta_{sp}}} - 1}{2{Ac}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

in Equation 2, A represents the Huggins constant, which was 0.247, and crepresents a concentration value, which was 1.2 g/dl.

(2) Melting temperature (Tm) and glass transition temperature (Tg): Tmand Tg of the polyester resins prepared in Examples and ComparativeExamples were measured by differential scanning calorimetry (DSC). Asthe measuring device, DSC 1 model (Mettler Toledo) was used.Specifically, the polyester resin sample to be used for the analysis wasdried under a nitrogen atmosphere at 120° C. for 5 to 10 hours using adehumidifying dryer (model name: D2T manufactured by Moretto).Therefore, Tm and Tg were measured in a state where the amount of waterremaining in the sample was less than 500 ppm.

<Tm Measurement>

About 6 to 10 mg of the dried sample was taken and filled in an aluminumpan. Then, the sample was kept at 30° C. for 3 minutes, heated from 30°C. to 280° C. at a rate of 10° C./min, and then the temperature wasmaintained at 280° C. for 3 minutes (first scan). Then, Tm peak (meltingpoint) value was analyzed in the first scan through the DSC using theintegration function in the TA menu of the related program (STAReSoftware) provided by Mettler Toledo. The first scan temperature rangewas set from onset point of −10° C. to Tm peak +10° C. calculated fromthe program.

<Tg Measurement>

After the first scan was performed in the same manner as in the methodfor measuring Tm, the sample was rapidly cooled to room temperature, andagain heated from room temperature to 280° C. at a rate of 10° C./min toobtain a DSC curve (second scan). Then, the Tg (glass transitiontemperature) value in the DSC 2^(nd) scan was analyzed through the glasstransition function in the DSC menu of the STARe Software. Herein, theTg is defined as the temperature at which the maximum slope of the curveappears at the point where the DSC curve obtained during the second scanchanges to a stair shape for the first time during the temperaturerising process. The temperature range of the scan was set from −20°C.−15° C. to 15° C.−20° C. of the midpoint calculated from the program.

(3) Molecular Weight

The molecular weight and the molecular weight distribution of thepolyester resin prepared in Examples and Comparative Examples weremeasured by GPC (Gel Permeation Chromatography). Specifically, 0.03 g ofa polyester resin to be tested for molecular weight was added to 3 mL ofo-chlorophenol, dissolved at 150° C. for 15 minutes, and then cooled toroom temperature, to which 9 mL of chloroform was added to prepare asample. Gel permeation chromatography of the sample was then performedusing two columns (Shodex LF 804) at a temperature of 40° C. and a flowrate of 0.7 mL/min. The weight average molecular weight (Mw) and thenumber average molecular weight (Mn) were respectively calculated usingpolystyrene as a standard material, and the molecular weightdistribution (PDI=Mw/Mn) was calculated from Mw and Mn.

(4) Haze

Specimens having a thickness of 6 mm were prepared by using thepolyester resins prepared in Examples and Comparative Examples, and thehaze of the specimens was measured using a CM-3600A measuring device(Minolta) according to ASTM D1003-97 test method.

(5) 1 Stage Bottle Molding:

A preform having a wall thickness of 4.5 mm and a height of 115 mm wasprepared by using the polyester resins prepared in Examples andComparative Examples with a 1 Stage Blow machine (NISSEI ASB) and thenmolded into a bottle having a height of 130 mm. Subsequently, thegeneration of haze was observed with the naked eye. If no haze wasobserved, it was indicated as ‘OK’, and if haze was observed, it wasindicated as ‘Haze’.

(6) 2 Stage Bottle Molding:

A preform having a wall thickness of 4.5 mm and a height of 100 mm wasprepared by using the polyester resin prepared in Examples andComparative Examples. Subsequently, the preform was molded into a bottlehaving a height of 210 mm through a heating/blowing process. If there isno abnormality in the 2 stage bottle molding process and no haze isobserved from the appearance of the finally molded product, it isindicated as ‘OK’, and if there is an abnormality in the molding processor a haze is observed from the appearance of the finally molded article,it is indicated as ‘NG’.

Example 1: Preparation of Polyester Resin

3222 g (19.4 mol) of terephthalic acid, 1155 g (18.6 mol) of ethyleneglycol, and 227 g (1.6 mol) of isosorbide were added to a 10 L reactorequipped with a column and a water-cooled condenser. 1.0 g of GeO₂ as acatalyst, 1.46 g of phosphoric acid as a stabilizer and 0.7 g of cobaltacetate as a coloring agent were used (molar ratio between dicarboxylicacid or its derivative and diol: 1:1.04). Then, nitrogen was injectedinto the reactor to create a pressurized state in which the pressure ofthe reactor was higher than the atmospheric pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 260° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

The pressure of the reactor was reduced to 5 Torr (absolute pressure: 5mmHg) at normal pressure for 30 minutes, and simultaneously thetemperature of the reactor was raised to 280° C. for 1 hour, and thepolycondensation reaction was carried out while maintaining the pressureof the reactor at 1 Torr (absolute pressure: 1 mmHg) or less. In theinitial stage of the polycondensation reaction, the stirring speed wasset to be quick, but with the proceeding of the polycondensationreaction, the stirring speed could be appropriately controlled when thestirring force was weakened due to an increase in the viscosity of thereactants, or when the temperature of the reactants was raised to theset temperature or more. The polycondensation reaction was carried outuntil the intrinsic viscosity (IV) of the mixture (melt) in the reactorreached 0.60 dl/g. When the intrinsic viscosity of the mixture in thereactor reached a desired level, the mixture was discharged to theoutside of the reactor and stranded, then it was solidified with acooling liquid and granulated so that the average weight was 12 to 14mg.

The particles were allowed to stand at 150° C. for 1 hour and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 200° C. at a rate of 40° C./hour andmaintained at 200° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.75 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 6 mol %, the residue derived fromethylene glycol was 91 mol % and the residue derived from diethyleneglycol was 3 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 236° C., Tg (2^(nd) scan) 85° C., Mn 19,000, Mw70,000, PDI 3.68 and haze 2.4%.

During molding of the 1 stage bottle using the polyester resin, haze wasnot observed with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Example 2: Preparation of Polyester Resin

3215 g (19.4 mol) of terephthalic acid, 1135 g (18.3 mol) of ethyleneglycol, and 240 g (1.6 mol) of isosorbide were added to a 10 L reactorequipped with a column and a water-cooled condenser. 1.0 g of GeO₂ as acatalyst, 1.46 g of phosphoric acid as a stabilizer, 0.7 g of cobaltacetate as a coloring agent and 100 ppm of trimellitic anhydride as abranching agent were used (molar ratio between dicarboxylic acid or itsderivative and diol: 1:1.03). Then, nitrogen was injected into thereactor to create a pressurized state in which the pressure of thereactor was higher than the atmospheric pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.for 2 hours. Then, the temperature of the reactor was maintained at 260°C. During this process, after confirming that 500 g of by-products weredischarged through the column and the condenser, 123 g (2.0 mol) ofethylene glycol was further added to the reactor. The mixture in thereactor was observed with the naked eye, and the temperature of thereactor was maintained at 260° C. until the mixture became transparent.When the esterification reaction was completed, the pressure in thereactor was reduced to normal pressure by discharging nitrogen in thepressurized reactor to the outside. Then, the mixture in the reactor wastransferred to a 7 L reactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 5 Torr (absolutepressure: 5 mmHg) at normal pressure for 30 minutes, and simultaneouslythe temperature of the reactor was raised to 280° C. for 1 hour, and thepolycondensation reaction was carried out while maintaining the pressureof the reactor at 1 Torr (absolute pressure: 1 mmHg) or less. In theinitial stage of the polycondensation reaction, the stirring speed wasset to be quick, but with the proceeding of the polycondensationreaction, the stirring speed could be appropriately controlled when thestirring force was weakened due to an increase in the viscosity of thereactants, or when the temperature of the reactants was raised to theset temperature or more. The polycondensation reaction was carried outuntil the intrinsic viscosity (IV) of the mixture (melt) in the reactorreached 0.65 dl/g. When the intrinsic viscosity of the mixture in thereactor reached a desired level, the mixture was discharged to theoutside of the reactor and stranded, then it was solidified with acooling liquid and granulated so that the average weight was 12 to 14mg.

The particles were allowed to stand at 150° C. for 1 hour and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 200° C. at a rate of 40° C./hour andmaintained at 200° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.95 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 6 mol %, the residue derived fromethylene glycol was 90 mol % and the residue derived from diethyleneglycol was 4 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 236° C., Tg (2^(nd) scan) 85° C., Mn 28,000, Mw95,000, PDI 3.39 and haze 1.2%.

During molding of the 1 stage bottle using the polyester resin, haze wasnot observed with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Example 3: Preparation of Polyester Resin

3387 g (20.4 mol) of terephthalic acid, 1176 g (19.0 mol) of ethyleneglycol, and 357 g (2.4 mol) of isosorbide were added to a 10 L reactorequipped with a column and a water-cooled condenser. 1.0 g of GeO₂ as acatalyst, 0.016 g of Polysynthrene Blue RLS (Clarient) as a blue toner,and 0.004 g of Solvaperm Red Red (Clarient) as a red toner were used(molar ratio between dicarboxylic acid or its derivative and diol:1:1.05). Then, nitrogen was injected into the reactor to create apressurized state in which the pressure of the reactor was higher thanthe atmospheric pressure by 1.0 kgf/cm² (absolute pressure: 1495.6mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 260° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 5 Torr (absolutepressure: 5 mmHg) at normal pressure for 30 minutes, and simultaneouslythe temperature of the reactor was raised to 280° C. for 1 hour, and thepolycondensation reaction was carried out while maintaining the pressureof the reactor at 1 Torr (absolute pressure: 1 mmHg) or less. In theinitial stage of the polycondensation reaction, the stirring speed wasset to be quick, but with the proceeding of the polycondensationreaction, the stirring speed could be appropriately controlled when thestirring force was weakened due to an increase in the viscosity of thereactants, or when the temperature of the reactants was raised to theset temperature or more. The polycondensation reaction was carried outuntil the intrinsic viscosity (IV) of the mixture (melt) in the reactorreached 0.60 dl/g. When the intrinsic viscosity of the mixture in thereactor reached a desired level, the mixture was discharged to theoutside of the reactor and stranded, then it was solidified with acooling liquid and granulated so that the average weight was 12 to 14mg. The particles thus obtained were stored in water at 70° C. for 5hours to remove unreacted raw materials contained in the particles.

The particles were allowed to stand at 140° C. for 3 hours and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 195° C. at a rate of 40° C./hour andmaintained at 195° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.85 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 10 mol %, the residue derived fromethylene glycol was 86.5 mol % and the residue derived from diethyleneglycol was 3.5 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 220° C., Tg (2^(nd) scan) 90° C., Mn 25,000, Mw83,000, PDI 3.32 and haze 1%.

During molding of the 1 stage bottle using the polyester resin, haze wasnot observed with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Example 4: Preparation of Polyester Resin

3824 g (19.7 mol) of dimethyl terephthalate, 2237 g (36.1 mol) ofethylene glycol, and 633 g (4.3 mol) of isosorbide were added to a 10 Lreactor equipped with a column and a water-cooled condenser. 1.5 g ofMn(II) acetate tetrahydrate and 1.8 g of Sb₂O₃ as a catalyst, 1.0 g ofphosphoric acid as a stabilizer and 1.1 g of cobalt acetate as acoloring agent were used (molar ratio between dicarboxylic acid or itsderivative and diol: 1:2.05). Then, nitrogen was injected into thereactor, but the pressure of the reactor was not allowed to increase(absolute pressure: 760 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 240° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 240° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the mixture in the reactor was transferred to a7 L reactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 5 Torr (absolutepressure: 5 mmHg) at normal pressure for 30 minutes, and simultaneouslythe temperature of the reactor was raised to 285° C. for 1 hour, and thepolycondensation reaction was carried out while maintaining the pressureof the reactor at 1 Torr (absolute pressure: 1 mmHg) or less. In theinitial stage of the polycondensation reaction, the stirring speed wasset to be quick, but with the proceeding of the polycondensationreaction, the stirring speed could be appropriately controlled when thestirring force was weakened due to an increase in the viscosity of thereactants, or when the temperature of the reactants was raised to theset temperature or more. The polycondensation reaction was carried outuntil the intrinsic viscosity (IV) of the mixture (melt) in the reactorreached 0.60 dl/g. When the intrinsic viscosity of the mixture in thereactor reached a desired level, the mixture was discharged to theoutside of the reactor and stranded, then it was solidified with acooling liquid and granulated so that the average weight was 12 to 14mg. The particles thus obtained were stored in water at 70° C. for 5hours to remove unreacted raw materials contained in the particles.

The particles were allowed to stand at 115° C. for 6 hours and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 205° C. at a rate of 40° C./hour andmaintained at 205° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.95 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 6 mol %, the residue derived fromethylene glycol was 91 mol % and the residue derived from diethyleneglycol was 3 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 236° C., Tg (2^(nd) scan) 85° C., Mn 27,000, Mw103,000, PDI 3.81 and haze 1.3%.

During molding of the 1 stage bottle using the polyester resin, haze wasnot observed with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Example 5: Preparation of Polyester Resin

3340 g (20.1 mol) of terephthalic acid, 104 g (0.63 mol) of isophthalicacid, 1248 g (20.1 mol) of ethylene glycol, and 242 g (1.7 mol) ofisosorbide were added to a 10 L reactor equipped with a column and awater-cooled condenser. 1.0 g of GeO₂ as a catalyst, 1.56 g ofphosphoric acid as a stabilizer, 0.012 g of Polysynthrene Blue RLS(Clarient) as a blue toner, and 0.004 g of Solvaperm Red Red (Clarient)as a red toner were used (molar ratio between dicarboxylic acid or itsderivative and diol: 1:1.05). Then, nitrogen was injected into thereactor to create a pressurized state in which the pressure of thereactor was higher than the atmospheric pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 255° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 255° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 5 Torr (absolutepressure: 5 mmHg) at normal pressure for 30 minutes, and simultaneouslythe temperature of the reactor was raised to 280° C. for 1 hour, and thepolycondensation reaction was carried out while maintaining the pressureof the reactor at 1 Torr (absolute pressure: 1 mmHg) or less. In theinitial stage of the polycondensation reaction, the stirring speed wasset to be quick, but with the proceeding of the polycondensationreaction, the stirring speed could be appropriately controlled when thestirring force was weakened due to an increase in the viscosity of thereactants, or when the temperature of the reactants was raised to theset temperature or more. The polycondensation reaction was carried outuntil the intrinsic viscosity (IV) of the mixture (melt) in the reactorreached 0.60 dl/g. When the intrinsic viscosity of the mixture in thereactor reached a desired level, the mixture was discharged to theoutside of the reactor and stranded, then it was solidified with acooling liquid and granulated so that the average weight was 12 to 14 mg

The particles were allowed to stand at 140° C. for 3 hours and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 200° C. at a rate of 40° C./hour andmaintained at 200° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.90 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 6 mol %, the residue derived fromethylene glycol was 90.5 mol % and the residue derived from diethyleneglycol was 3.5 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 236° C., Tg (2^(nd) scan) 85° C., Mn 27,000, Mw87,000, PDI 3.22 and haze 1.2%.

During molding of the 1 stage bottle using the polyester resin, haze wasnot observed with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Example 6: Preparation of Polyester Resin

3250 g (19.6 mol) of terephthalic acid, 1093 g (17.6 mol) of ethyleneglycol, and 400 g (2.7 mol) of isosorbide were added to a 10 L reactorequipped with a column and a water-cooled condenser. 1.0 g of GeO₂ as acatalyst, 1.56 g of phosphoric acid as a stabilizer, 0.016 g ofPolysynthrene Blue RLS (Clarient) as a blue toner, 0.004 g of SolvapermRed Red (Clarient) as a red toner, 1 ppm of polyethylene as acrystallizing agent, and 100 ppm of Iganox 1076 as an antioxidant wereused (molar ratio between dicarboxylic acid or its derivative and diol:1:1.04). Then, nitrogen was injected into the reactor to create apressurized state in which the pressure of the reactor was higher thanthe atmospheric pressure by 0.5 kgf/cm² (absolute pressure: 1127.8mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 255° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 255° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 100 Torr (absolutepressure: 100 mmHg) at normal pressure for 10 minutes, and this pressurestate was maintained for 1 hour. Then, the temperature of the reactorwas raised to 275° C. for 1 hour, and the polycondensation reaction wascarried out while maintaining the pressure of the reactor at 1 Torr(absolute pressure: 1 mmHg) or less. In the initial stage of thepolycondensation reaction, the stirring speed was set to be quick, butwith the proceeding of the polycondensation reaction, the stirring speedcould be appropriately controlled when the stirring force was weakeneddue to an increase in the viscosity of the reactants, or when thetemperature of the reactants was raised to the set temperature or more.The polycondensation reaction was carried out until the intrinsicviscosity (IV) of the mixture (melt) in the reactor reached 0.50 dl/g.When the intrinsic viscosity of the mixture in the reactor reached adesired level, the mixture was discharged to the outside of the reactorand stranded, then it was solidified with a cooling liquid andgranulated so that the average weight was 12 to 14 mg

The particles were allowed to stand at 140° C. for 3 hours and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 190° C. at a rate of 40° C./hour andmaintained at 190° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.70 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 12 mol %, the residue derived fromethylene glycol was 83 mol % and the residue derived from diethyleneglycol was 5 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 210° C., Tg (2^(nd) scan) 90° C., Mn 22,000, Mw68,000, PDI 3.09 and haze 0.8%.

During molding of the 1 stage bottle using the polyester resin, haze wasnot observed with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Example 7: Preparation of Polyester Resin

3231 g (19.5 mol) of terephthalic acid, 1098 g (17.7 mol) of ethyleneglycol, and 398 g (2.7 mol) of isosorbide were added to a 10 L reactorequipped with a column and a water-cooled condenser. 1.0 g of GeO₂ as acatalyst, 1.50 g of phosphoric acid as a stabilizer, 0.020 g ofPolysynthrene Blue RLS (Clarient) as a blue toner, and 0.004 g ofSolvaperm Red Red (Clarient) as a red toner were used (molar ratiobetween dicarboxylic acid or its derivative and diol: 1:1.05). Then,nitrogen was injected into the reactor to create a pressurized state inwhich the pressure of the reactor was higher than the atmosphericpressure by 0.5 kgf/cm² (absolute pressure: 1127.8 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 255° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 255° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 5 Torr (absolutepressure: 5 mmHg) at normal pressure for 30 minutes, and this pressurestate was maintained for 1 hour. Then, the temperature of the reactorwas raised to 270° C. for 1 hour, and the polycondensation reaction wascarried out while maintaining the pressure of the reactor at 1 Torr(absolute pressure: 1 mmHg) or less. In the initial stage of thepolycondensation reaction, the stirring speed was set to be quick, butwith the proceeding of the polycondensation reaction, the stirring speedcould be appropriately controlled when the stirring force was weakeneddue to an increase in the viscosity of the reactants, or when thetemperature of the reactants was raised to the set temperature or more.The polycondensation reaction was carried out until the intrinsicviscosity (IV) of the mixture (melt) in the reactor reached 0.70 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 12 mol %, the residue derived fromethylene glycol was 86 mol % and the residue derived from diethyleneglycol was 2 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 210° C., Tg (2^(nd) scan) 92° C., Mn 22,000, Mw68,000, PDI 3.09 and haze 0.8%.

During molding of the 1 stage bottle using the polyester resin, haze wasnot observed with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Comparative Example 1: Preparation of Polyester Resin

3302 g (19.9 mol) of terephthalic acid and 1480 g (23.9 mol) of ethyleneglycol were added to a 10 L reactor equipped with a column and awater-cooled condenser. 1.0 g of GeO₂ as a catalyst, 1.46 g ofphosphoric acid as a stabilizer, 0.012 g of Polysynthrene Blue RLS(Clarient) as a blue toner, and 0.004 g of Solvaperm Red Red (Clarient)as a red toner were used (molar ratio between dicarboxylic acid or itsderivative and diol: 1:1.2). Then, nitrogen was injected into thereactor to create a pressurized state in which the pressure of thereactor was higher than the atmospheric pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 260° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 5 Torr (absolutepressure: 5 mmHg) at normal pressure for 30 minutes, and simultaneouslythe temperature of the reactor was raised to 280° C. for 1 hour, and thepolycondensation reaction was carried out while maintaining the pressureof the reactor at 1 Torr (absolute pressure: 1 mmHg) or less. In theinitial stage of the polycondensation reaction, the stirring speed wasset to be quick, but with the proceeding of the polycondensationreaction, the stirring speed could be appropriately controlled when thestirring force was weakened due to an increase in the viscosity of thereactants, or when the temperature of the reactants was raised to theset temperature or more. The polycondensation reaction was carried outuntil the intrinsic viscosity (IV) of the mixture (melt) in the reactorreached 0.60 dl/g. When the intrinsic viscosity of the mixture in thereactor reached a desired level, the mixture was discharged to theoutside of the reactor and stranded, then it was solidified with acooling liquid and granulated so that the average weight was 12 to 14mg.

The particles were allowed to stand at 150° C. for 1 hours and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 210° C. at a rate of 40° C./hour andmaintained at 210° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.80 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from ethylene glycol was 96.5 mol % and the residuederived from diethylene glycol was 3.5 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 250° C., Tg (2^(nd) scan) 70° C., Mn 23,000, Mw75,000, PDI 3.26 and haze 10.4%.

During molding of the 1 stage bottle using the polyester resin, haze wasobserved with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Comparative Example 2: Preparation of Polyester Resin

3492 g (21.0 mol) of terephthalic acid, 1748 g (28.2 mol) of ethyleneglycol, and 184 g (1.3 mol) of isosorbide were added to a 10 L reactorequipped with a column and a water-cooled condenser. 1.0 g of GeO₂ as acatalyst, 1.46 g of phosphoric acid as a stabilizer, and 0.7 g of cobaltacetate as a coloring agent were used (molar ratio between dicarboxylicacid or its derivative and diol: 1:1.4). Then, nitrogen was injectedinto the reactor to create a pressurized state in which the pressure ofthe reactor was higher than the atmospheric pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 260° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 5 Torr (absolutepressure: 5 mmHg) at normal pressure for 30 minutes, and simultaneouslythe temperature of the reactor was raised to 280° C. for 1 hour, and thepolycondensation reaction was carried out while maintaining the pressureof the reactor at 1 Torr (absolute pressure: 1 mmHg) or less. In theinitial stage of the polycondensation reaction, the stirring speed wasset to be quick, but with the proceeding of the polycondensationreaction, the stirring speed could be appropriately controlled when thestirring force was weakened due to an increase in the viscosity of thereactants, or when the temperature of the reactants was raised to theset temperature or more. The polycondensation reaction was carried outuntil the intrinsic viscosity (IV) of the mixture (melt) in the reactorreached 0.60 dl/g. When the intrinsic viscosity of the mixture in thereactor reached a desired level, the mixture was discharged to theoutside of the reactor and stranded, then it was solidified with acooling liquid and granulated so that the average weight was 12 to 14mg.

The particles were allowed to stand at 140° C. for 3 hours and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 205° C. at a rate of 40° C./hour andmaintained at 205° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.75 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 3 mol %, the residue derived fromethylene glycol was 94 mol % and the residue derived from diethyleneglycol was 3 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1I′ scan was 240° C., Tg (2^(nd) scan) 82° C., Mn 20,000, Mw72,000, PDI 3.60 and haze 5.5%.

During molding of the 1 stage bottle using the polyester resin, haze wasobserved with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Comparative Example 3: Preparation of Polyester Resin

3355 g (20.2 mol) of terephthalic acid, 1228 g (19.8 mol) of ethyleneglycol, and 207 g (1.4 mol) of isosorbide were added to a 10 L reactorequipped with a column and a water-cooled condenser. 1.0 g of GeO₂ as acatalyst, 1.46 g of phosphoric acid as a stabilizer, and 0.7 g of cobaltacetate as a coloring agent were used (molar ratio between dicarboxylicacid or its derivative and diol: 1:1.05). Then, nitrogen was injectedinto the reactor to create a pressurized state in which the pressure ofthe reactor was higher than the atmospheric pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 260° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 5 Torr (absolutepressure: 5 mmHg) at normal pressure for 30 minutes, and simultaneouslythe temperature of the reactor was raised to 280° C. for 1 hour, and thepolycondensation reaction was carried out while maintaining the pressureof the reactor at 1 Torr (absolute pressure: 1 mmHg) or less. In theinitial stage of the polycondensation reaction, the stirring speed wasset to be quick, but with the proceeding of the polycondensationreaction, the stirring speed could be appropriately controlled when thestirring force was weakened due to an increase in the viscosity of thereactants, or when the temperature of the reactants was raised to theset temperature or more. The polycondensation reaction was carried outuntil the intrinsic viscosity (IV) of the mixture (melt) in the reactorreached 0.40 dl/g. When the intrinsic viscosity of the mixture in thereactor reached a desired level, the mixture was discharged to theoutside of the reactor and stranded, then it was solidified with acooling liquid and granulated so that the average weight was 12 to 14mg.

The particles were allowed to stand at 150° C. for 1 hour and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 200° C. at a rate of 40° C./hour andmaintained at 200° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.75 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 6 mol %, the residue derived fromethylene glycol was 92 mol % and the residue derived from diethyleneglycol was 2 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 237° C., Tg (2^(nd) scan) 85° C., Mn 18,000, Mw75,000, PDI 4.17 and haze 3.50/%.

During molding of the 1 stage bottle using the polyester resin, haze wasobserved with the naked eye. There was no problem in moldability andappearance even in 2 stage bottle molding.

Comparative Example 4: Preparation of Polyester Resin

2652 g (16.0 mol) of terephthalic acid, 1278 g (20.6 mol) of ethyleneglycol, and 257 g (1.8 mol) of isosorbide were added to a 10 L reactorequipped with a column and a water-cooled condenser. 1.0 g of GeO₂ as acatalyst, 1.46 g of phosphoric acid as a stabilizer, 0.010 g ofPolysynthrene Blue RLS (Clarient) as a blue toner, 0.003 g of SolvapermRed Red (Clarient) as a red toner, and 1 ppm of polyethylene as acrystallizing agent were used (molar ratio between dicarboxylic acid orits derivative and diol: 1:1.4). Then, nitrogen was injected into thereactor to create a pressurized state in which the pressure of thereactor was higher than the atmospheric pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 260° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 260° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 5 Torr (absolutepressure: 5 mmHg) at normal pressure for 30 minutes, and simultaneouslythe temperature of the reactor was raised to 270° C. for 1 hour, and thepolycondensation reaction was carried out while maintaining the pressureof the reactor at 1 Torr (absolute pressure: 1 mmHg) or less. In theinitial stage of the polycondensation reaction, the stirring speed wasset to be quick, but with the proceeding of the polycondensationreaction, the stirring speed could be appropriately controlled when thestirring force was weakened due to an increase in the viscosity of thereactants, or when the temperature of the reactants was raised to theset temperature or more. The polycondensation reaction was carried outuntil the intrinsic viscosity (IV) of the mixture (melt) in the reactorreached 0.50 dl/g. When the intrinsic viscosity of the mixture in thereactor reached a desired level, the mixture was discharged to theoutside of the reactor and stranded, then it was solidified with acooling liquid and granulated so that the average weight was 12 to 14mg.

The particles were allowed to stand at 140° C. for 3 hour and subjectedto crystallization, and then added to a 20 L solid phase polymerizationreactor. Thereafter, nitrogen was flowed into the reactor at a rate of50 L/min. At this time, the temperature of the reactor was raised fromroom temperature to 140° C. at a rate of 40° C./hour, maintained at 140°C. for 3 hours, then raised to 200° C. at a rate of 40° C./hour andmaintained at 200° C. The solid phase polymerization was carried outuntil the intrinsic viscosity (IV) of the particles in the reactorreached 0.95 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 6 mol %, the residue derived fromethylene glycol was 88 mol % and the residue derived from diethyleneglycol was 6 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was 230° C., Tg (2^(nd) scan) 82° C., Mn 26,000, Mw107,000, PDI 4.12 and haze 1.5%.

Comparative Example 5: Preparation of Polyester Resin

3325 g (20.0 mol) of terephthalic acid, 1143 g (18.4 mol) of ethyleneglycol, and 1111 g (7.6 mol) of isosorbide were added to a 10 L reactorequipped with a column and a water-cooled condenser. 1.0 g of GeO₂ as acatalyst, 1.50 g of phosphoric acid as a stabilizer, 0.021 g ofPolysynthrene Blue RLS (Clarient) as a blue toner, 0.004 g of SolvapermRed Red (Clarient) as a red toner, and 10 ppm of Iganox 1076 as anantioxidant were used (molar ratio between dicarboxylic acid or itsderivative and diol: 1:1.3). Then, nitrogen was injected into thereactor to create a pressurized state in which the pressure of thereactor was higher than the atmospheric pressure by 1.0 kgf/cm²(absolute pressure: 1495.6 mmHg).

Then, the temperature of the reactor was raised to 220° C. for 90minutes, maintained at 220° C. for 2 hours, and then raised to 255° C.for 2 hours. Thereafter, the mixture in the reactor was observed withthe naked eye, and the esterification reaction was carried out whilemaintaining the temperature of the reactor at 255° C. until the mixturebecame transparent. During this process, 650 g of by-products weredischarged through the column and the condenser. When the esterificationreaction was completed, the pressure in the reactor was reduced tonormal pressure by discharging nitrogen in the pressurized reactor tothe outside. Then, the mixture in the reactor was transferred to a 7 Lreactor capable of performing a vacuum reaction.

Then, the pressure of the reactor was reduced to 100 Torr (absolutepressure: 100 mmHg) at normal pressure for 10 minutes, and this pressurestate was maintained for 1 hour. Then, the temperature of the reactorwas raised to 270° C. for 1 hour, and the polycondensation reaction wascarried out while maintaining the pressure of the reactor at 1 Torr(absolute pressure: 1 mmHg) or less. In the initial stage of thepolycondensation reaction, the stirring speed was set to be quick, butwith the proceeding of the polycondensation reaction, the stirring speedcould be appropriately controlled when the stirring force was weakeneddue to an increase in the viscosity of the reactants, or when thetemperature of the reactants was raised to the set temperature or more.The polycondensation reaction was carried out until the intrinsicviscosity (IV) of the mixture (melt) in the reactor reached 0.70 dl/g.

With respect to the total acid-derived residue contained in thepolyester resin thus prepared, the residue derived from terephthalicacid was 100 mol %. With respect to the total diol-derived residue, theresidue derived from isosorbide was 20 mol %, the residue derived fromethylene glycol was 77.5 mol % and the residue derived from diethyleneglycol was 2.5 mol %.

As a result of measuring the physical properties of the polyester resinaccording to the above-mentioned methods, it was confirmed that Tm inthe DSC 1^(st) scan was not observed, Tg (2^(nd) scan) 95° C., Mn25,000, Mw 68,000, PDI 2.72 and haze 0.8%.

During molding of the 1 stage bottle using the polyester resin, haze wasnot observed with the naked eye. There was a problem in moldability andappearance even in 2 stage bottle molding.

Experimental Example: Evaluation of Polyester Resin

The physical properties of the polyester resins prepared in Examples 1to 7 and Comparative Examples 1 to 5 were evaluated according to themethods described above, and the results are shown in Table 1.

TABLE 1 Difference ISB between ISB G/A residual melt IV content Mn 1stage 2 stage I/T ratio and solid DEG Tg Mw bottle bottle E/T (%) phaseIV content Tm PDI Haze molding molding Example 1 1.04 75 0.15 6 mol % 85° C. 19,000 2.4% OK OK 0.08 3 mol % 236° C. 70,000 0.96 3.68 2 1.1371 0.30 6 mol %  85° C. 28,000 1.2% OK OK (1.03 + 0.1) 4 mol % 236° C.95,000 0.085 3.39 0.945 3 1.05 83 0.25 10 mol %   90° C. 25,000 1.0% OKOK 0.12 3.5 mol %   220° C. 83,000 0.93 3.32 4 2.050 27 0.35 6 mol % 85° C. 27,000 1.3% OK OK 0.220 3 mol % 236° C. 103,000 1.830 3.81 5 .0575 0.30 6 mol %  85° C. 27,000 1.2% OK OK 0.080 3.5 mol %   236° C.87,000 0.97 3.22 6 1.04 86 0.20 12 mol %   90° C. 22,000 0.8% OK OK 0.145 mol % 210° C. 68,000 0.9 3.09 7 1.05 86 — 12 mol %   92° C. 23,0000.7% OK OK 0.14 2 mol % 212° C. 65,000 0.91 2.83 Comparative 1 1.200 —0.20 0 mol %  70° C. 23,000 10.4% Haze OK Example 0.000 3.5 mol %   250°C. 75,000 1.200 3.26 2 1.400 50 0.15 3 mol %  82° C. 20,000 5.5% Haze OK0.060 3 mol % 240° C. 72,000 1.340 3.60 3 1.050 86 0.35 6 mol %  85° C.18,000 3.5% Haze OK 0.070 2 mol % 237° C. 75,000 0.980 4.17 4 1.400 550.45 6 mol %  82° C. 26,000 1.5% Progressing the 0.110 6 mol % 230° C.107,000 molding X 1.290 4.12 5 1.300 54 — 20 mol %   95° C. 25,000 0.8%OK NG 0.380 2.5 mol %   — 68,000 0.920 2.72 GIA: Molar ratio of diol todicarboxylic acid or its derivative (mole number of the diol/mole numberof the dicarboxylic acid or its derivative; when the diol is added/mixedin a plurality of steps, it is separately described in the form of“initial mixing molar ratio of diol + additional addition molar ratio”in parentheses). I/T: Molar ratio of isosorbide to dicarboxylic acid orits derivative (mole number of isosorbide/mole number of dicarboxylicacid or derivative thereof) E/T: Molar ratio of ethylene glycol todicarboxylic acid or its derivative (mole number of ethylene glycol/molenumber of dicarboxylic acid or derivative thereof) ISB residual ratio:Molar ratio of isosorbide introduced into the polyester resin relativeto the total isosorbide used for the preparation of the polyester resin({mole number of diol moiety derived from isosorbide/mole number of acidmoiety derived from dicarboxylic acid or derivative thereof}/{molenumber of isosorbide/mole number of dicarboxylic acid or derivativethereof} * 100) Differences between melt IV and solid phase IV:Difference between the intrinsic viscosity of resin beforepolycondensation reaction completion and solid phase polymerization(molt IV) and the intrinsic viscosity of the resin after solid phasepolymerization (solid phase IV) ISB content: The molar ratio of theresidue derived from isosorbide relative to the residue derived fromtotal diols included in the polyester resin DEG content: The molar ratioof the residue derived from diethylene glycol relative to the residuederived from total diols included in the polyester resin

Referring to Table 1, in the 1 stage bottle molding process, blowing isperformed by using the latent heat of the molded preform. However, ifthe diol moiety derived from isosorbide is not contained as in thepolyester resin of Comparative Example 1, it is confirmed that haze isgenerated due to intramolecular crystallization at a temperaturesuitable for progressing the blowing. If the molded preform issufficiently cooled in order to prevent the generation of haze, aproblem arises that the subsequent blowing becomes impossible.

In addition, it is confirmed that the polyester resin of ComparativeExample 2 contains a too small amount of the diol portion derived fromisosorbide and thus haze is generated after molding due to highregularity of the polymer chain.

On the other hand, referring to Example 1, Example 2, and ComparativeExample 3, it is confirmed that although the polyester resin includesdiol moieties derived from the same content of isosorbide, haze isgenerated when the content of diol moieties derived from diethyleneglycol relative to the total diol moiety is less than 2.5 mole % andwhen the molecular weight distribution is more than 4. In particular, itis confirmed from Examples 1 and 2 and Comparative Example 3 that theintrinsic viscosity of the resin before solid phase polymerization (meltIV) should be at least 0.45 dl/g, whereby in order not to cause haze, anappropriate amount of a diol moiety derived from diethylene glycol canbe included and an appropriate molecular weight distribution can beexhibited.

On the other hand, referring to Comparative Example 4, it is confirmedthat although the polyester resin contains an appropriate amount of adiol moiety derived from isosorbide, the heat resistance is lowered ifit contains a large amount of the diol moiety derived from diethyleneglycol. Considering that Tg required for applications such as a hot filljar is at least about 85° C., it can be seen that the polyester resinproduced from Comparative Example 4 is unsuitable for applications suchas a hot fill jar.

On the other hand, referring to Example 6, Example 7, and ComparativeExample 5, it can be confirmed that there is a limit in the monomercomposition for providing a polyester resin having a melting pointduring the first scan through DSC. In the case of the polyester resin ofComparative Example 5 in which the diol moiety derived from isosorbideis 20 mol % based on the entire diol moiety derived from the diol, Tmpeak is not observed during the first scan through DSC, wherebyorientation due to drawing of molecules does not occur. Therefore, it isconfirmed that in the case of the polyester resin of Comparative Example5, a two stage bottle molding in which a draw ratio of the preform andthe bottle is large as described above is impossible.

Thereby, it is confirmed that the polyester resin is prepared underspecific process conditions, such as the initial input/mixing ratio ofthe diol being controlled in an appropriate range, the diol moietyderived from isosorbide and the diol moiety derived from diethyleneglycol in the polymer chain must satisfy a specific range to have aglass transition temperature above a certain level, thereby exhibitinghigh heat resistance and excellent mechanical properties, and showinghigh transparency despite its thick wall thickness. Further, it isconfirmed that by adjusting the intrinsic viscosity of the resin beforethe solid phase polymerization reaction and adjusting the molecularweight distribution of the polyester resin to be narrow, an appropriatecrystallization speed can be achieved, thereby providing a thick resinmolded article without causing haze.

It can be confirmed that the resin molded articles prepared from thepolyester resins of all of the above Examples exhibit very low haze ofless than 3% despite their thick wall thickness, have a melting pointduring the first scan through DSC and have a high glass transitiontemperature, so that both 1 and 2 stage bottle molding are possible andit is effective to be applied to various applications such as bottle.

What is claimed is:
 1. A polyester resin polymerized with a dicarboxylicacid including terephthalic acid or a derivative thereof and a diolincluding isosorbide and ethylene glycol, thereby having an alternatingstructure of an acid moiety derived from the dicarboxylic acid or aderivative thereof and a diol moiety derived from the diol, wherein thepolyester resin includes 6 to 12 mol % of a diol moiety derived fromisosorbide and 2 to 5 mol % of a diol moiety derived from diethyleneglycol based on the total diol moieties derived from the diol, wherein amelting point exists during the first scan through a differentialscanning calorimetry (DSC), and wherein a haze is less than 3% asmeasured according to ASTM D1003-97 for a specimen having a thickness of6 mm obtained from the polyester resin.
 2. The polyester resin of claim1, wherein the haze is 1.5% or less as measured according to ASTMD1003-97 for a specimen having a thickness of 6 mm obtained from thepolyester resin.
 3. The polyester resin of claim 1, wherein thedicarboxylic acid or a derivative thereof is a dicarboxylic acid or aderivative thereof other than terephthalic acid or a derivative thereof,which includes at least one selected from the group consisting of anaromatic dicarboxylic acid having 8 to 14 carbon atoms or a derivativethereof and an aliphatic dicarboxylic acid having 4 to 12 carbon atomsor a derivative thereof in an amount of 0 to 50 mol % based on the totaldicarboxylic acids or derivatives thereof.
 4. The polyester resin ofclaim 1, wherein the polyester resin has a number average molecularweight of 15,000 to 50,000 g/mol.
 5. The polyester resin of claim 1,wherein the polyester resin has a weight average molecular weight of50,000 to 150,000 g/mol.
 6. The polyester resin of claim 1, wherein thepolyester resin has a molecular weight distribution of 2.5 to 4.0. 7.The polyester resin of claim 1, wherein the polyester resin has amelting point of 200° C. to 250° C. as measured during the first scanthrough a differential scanning calorimetry (DSC).
 8. The polyesterresin of claim 1, wherein the polyester resin has a glass transitiontemperature of 85° C. or more.
 9. The polyester resin of claim 1,wherein the polyester resin is used for a bottle, a hot fill jar, ahigh-pressure vessel, a sheet, a drawn film or a fiber.
 10. A method forpreparing a polyester resin comprising the steps of: (a) carrying out anesterification reaction or a transesterification reaction of (i) adicarboxylic acid or a derivative thereof including terephthalic acid ora derivative thereof and (ii) a diol including 6.5 mol to 25 mol ofisosorbide and 80 mol to 200 mol of ethylene glycol based on 100 mol ofthe total dicarboxylic acid or a derivative thereof; and (b) subjectingthe esterification or transesterification reaction product to apolycondensation reaction so that an intrinsic viscosity, which ismeasured at 35° C. after dissolving the reaction product inorthochlorophenol at a concentration of 1.2 g/dl at 150° C. for 15minutes, reaches 0.45 dl/g to 0.75 dl/g.
 11. The method of preparing apolyester resin of claim 10, wherein the (i) dicarboxylic acid or aderivative thereof is a dicarboxylic acid, and the initial mixing molarratio of the (i) dicarboxylic acid: the (ii) diol is adjusted to 1:1.01to 1.05, or the (i) dicarboxylic acid or a derivative thereof is adicarboxylic acid alkyl ester or a dicarboxylic acid anhydride, and theinitial mixing molar ratio of the (i) dicarboxylic acid derivative: the(ii) diol is adjusted to 1:2.0 to 1:2.1.
 12. The method of preparing apolyester resin of claim 10, wherein a part of the (ii) diol is furtheradded during the reaction.
 13. The method of preparing a polyester resinof claim 10, wherein a polycondensation catalyst, a stabilizer, acoloring agent, a crystallizing agent, an antioxidant or a branchingagent is added to the slurry before the start of the (a) esterificationreaction or the transesterification reaction, or to the product afterthe completion of the reaction.
 14. The method of preparing a polyesterresin of claim 10, further comprising removing unreacted materialsincluding isosorbide by allowing the product obtained by theesterification reaction or the transesterification reaction to standunder a reduced pressure condition of 400 to 1 mmHg for 0.2 to 3 hours,before the (b) polycondensation reaction.
 15. The method of preparing apolyester resin of claim 10, further comprising, after step (b), (c) astep of crystallizing the polymer prepared by the polycondensationreaction; and (d) a step of subjecting the crystallized polymer to asolid phase polymerization such that the intrinsic viscosity, which ismeasured at 35° C. after dissolving the polymer in orthochlorophenol ata concentration of 1.2 g/dl at 150° C. for 15 minutes, reaches a valueof 0.10 to 0.40 dl/g higher than the intrinsic viscosity of the resinobtained in step (b).
 16. A resin molded article prepared from thepolyester resin according to claim
 1. 17. The resin molded article ofclaim 16, having a wall thickness of 4.5 mm or more.
 18. The method ofpreparing a polyester resin of claim 11, wherein a part of the (ii) diolis further added during the reaction.